System and method of computer operating mode clock control for power consumption reduction

ABSTRACT

A power management unit for use in a computer system includes an activity monitor which monitors activity of the computer system and generates an activity indicator signal reflective of the monitored activity, a mode controller responsive to the activity indicator signal and having at least three operating modes, and a power switching circuit having a plurality of power control signal lines each for controlling one of the plurality of power control switches.

CROSS REFERENCE RELATED U.S. PATENT APPLICATION

This is a continuation of application Ser. No. 09/121,352 filed Jul. 23, 1998, U.S. Pat. No. 6,079,025; which is a division of application Ser. No. 08/767,821 filed Dec. 17, 1996, abandoned; which is a continuation of application Ser. No. 08/460,191 filed Jun. 2, 1995, abandoned; which is a continuation of application Ser. No. 08/285,169 filed Aug. 3, 1994, abandoned; which is a continuation of application Ser. No. 08/017,975 filed Feb. 12, 1993, U.S. Pat. No. 5,396,635; which is a continuation of application Ser. No. 07/908,533 filed Jun. 29, 1992, abandoned, which is a continuation of application Ser. No. 07/532,314 filed Jun. 1, 1990, abandoned.

BACKGROUND OF THE INVENTION

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

The present invention relates to computers and particularly to methods and apparatus for power management in computers, particularly in battery-powered computers.

The major parts of computers include a central processing unit (CPU), input/output (I/O) devices such as display screens, keyboards, modems, printers, disk drives and the like, and storage (memory).

The CPU communicates with the I/O devices, with the storage and otherwise operates with addresses defined within the computer address range. Typically, addresses for I/O devices are within an I/O address range. Addresses for execution of programs without I/O reference typically are within a memory address range. Similarly, that portion of memory allocated for display is within a video memory address range.

Computers function to execute application programs such as word processing, spreadsheet and data base management programs. Typically, the computer and the application programs are under the control of a software operating system that manages the different system parts and resources including some I/O devices. For example, during the execution of an application program when the CPU wishes to check to determine if any key has been depressed on the keyboard, the CPU through a subroutine call to the operating system requests the operating system through execution of a subroutine to perform a key-actuation detection task. Since the operating system performs many such tasks, the operating system has a detailed knowledge of many activities within the computer. However, under some circumstances, application programs bypass the operating system and directly address I/O devices. Typically, each I/O device is assigned an I/O address within an I/O address range. For application programs which-directly address I/O devices without operating system calls, the operating system is not immediately aware of I/O activity. With such complex operation in computers, the task of power conservation is difficult.

The need for power conservation is well known in battery-powered computers and must be performed in a manner that does not interfere with the operation of the computer or impede users from interacting with the computer during the execution of application programs.

Conservation of power has been utilized for some parts of battery-powered computers but has been ignored for other parts of such computers. In general, power consumption is distributed in battery-powered computers among the major parts of those computers. One part with significant power consumption is the central processing unit (CPU). Another part is the input/output (I/O) devices such as display screens, keyboards, modems, printers, disk drives and the like. Still another part with significant power consumption is storage (memory).

Prior art attempts at conserving power have employed screen blanking which reduces the power to the display screen when the screen has not been used for some period of time. Typically, a timeout circuit senses changes in screen information and, if no change has occurred for a predetermined timeout period, the backlight to the screen is turned off for power reduction. While screen blanking is effective in reducing power for the display screen, no reduction results in power to the driver circuitry for the display, to the CPU, or to other parts of the computer. Furthermore, when the screen is blanked, the computer cannot be used until reset.

Other prior art attempts at conserving power consumption have focused on disk drives because the power consumption of rotating magnetic disks is high. Disk drive manufacturers have employed various schemes for reducing the power consumption of the disk drive. While such power consumption schemes are effective for the disk drive, no reduction results in power to the CPU or other parts of the computer. Computers without disk drives, such as small “notebook” computers, have no need, of course, for the conservation of power in a disk drive.

In order to extend the battery life of portable computers and to manage power in computers, there is a need for improved power management methods and apparatus in computers, particularly for power management that can be extended to many different parts and conditions of the computer.

SUMMARY OF THE INVENTION

The present invention is a method and apparatus for power management in a computer. The computer typically includes as hardware a central processing unit (CPU), storage (memory) and I/O devices and includes as software an operating system adapted to control the computer during application program execution.

The power management method and apparatus causes the computer system to enter the power conservation mode after sensing inactivity by a software monitor or by a hardware monitor.

The software monitor monitors the activity of the operating system or other software in the system. The software monitor typically is a software module linked, for example, to the operating system at boot time for monitoring subroutine calls to the operating system.

The hardware monitor monitors the hardware to detect inactivity. The hardware monitor typically is circuitry for detecting inactivity independently from the software. For example, the hardware monitor senses predetermined address ranges, such as an I/O address range and a video memory address range, and monitors the activity of addresses by the CPU to addresses within these ranges. If no data transfers occur within the specified address ranges for predetermined periods of time, then a power conservation mode is entered to conserve power in the computer system.

By using both a software monitor and a hardware monitor, the power management unit determines exactly when to enter into power conservation mode without sacrificing system performance.

In the software monitor, inactivity is determined by detecting how many “active” or “idle” function calls an application makes within some time period. In the IBM PC DOS environment, the activity status is checked, for example, no less frequently than every 50 milliseconds. There are 256 IBM PC DOS function calls and, in principle, each is labeled as “idle” or “active” and each is assigned a corresponding positive or negative number. A positive number is assigned to an “active” function call and a negative number to an “idle” function call.

The power management software monitor forms an activity measurement as a running total of the function call numbers as the function calls are made. Whenever a function call is made (either active or conservation), the power management software monitor algebraically adds the function call number to the accumulated value and determines whether the system is to remain in the active mode or be switched to the conservation mode by comparing the magnitude of the accumulated value with a function call threshold.

The function call threshold for determining activity is a variable depending on the computer system speed. To prevent the system from oscillating between the active and conservation mode due to minor changes in system activity, hysterisis is provided by using active and conservation function call thresholds. The accumulated total for the activity measurement is reset after it reaches the active threshold going in one direction or the conservation threshold going in the opposite direction as the case may be.

The active and conservation thresholds are typically unequal so that the entry and exit from conservation mode is biased. For example, in order to have the system enter the conservation mode quickly and thereby to reduce power consumption, the active threshold is set with a number greater than the number for the conservation threshold.

In one embodiment, functions that require immediate attention are assigned numbers large relative to the active and idle thresholds so that a single occurrence of the function call will force the accumulated count over the active threshold and thus force the system to be in the active mode. The hysterisis effect can be bypassed by forcing the power management unit into active mode without changing the activity count. In this case, the next idle function call will bring the system back to idle mode.

If the software monitor or the hardware monitor indicates inactivity, the power management unit enters the conservation mode. The conservation mode has multiple states which provide different levels of power conservation.

A first state, called a DOZE state, is entered after sensing inactivity by the hardware monitor for a first period of time. A second state, called a SLEEP state, is entered after sensing inactivity by the hardware monitor for a second predetermined time where the second predetermined time is greater than the first predetermined time. A third state, called a SUSPEND state, is entered after sensing inactivity by the hardware monitor for a third period of time greater than the first and second time periods.

Another state is OFF which turns off all power for the computer under predetermined conditions.

During periods of inactivity, power consumption is reduced in different ways, for example, by reducing clock speeds or removing clocks, and/or by removing power, and/or by controlling the refresh frequency to memory.

In accordance with the above summary, the present invention achieves the objective of providing an improved power management method and apparatus.

The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of a computer with the power management unit of the present invention.

FIG. 2 depicts a block diagram of the power management unit of the FIG. 1 system.

FIG. 3 depicts a detailed block diagram of the hardware for the power management unit of FIG. 2.

FIG. 4 depicts a state diagram depicting the multiple states associated with the power management unit of FIGS. 1, 2 and 3 as determined by the hardware monitor.

FIG. 5 depicts a representation of operation for various states as a function of the activity measurement.

FIG. 6 depicts a state diagram depicting switching to conservation mode (DOZE or SLEEP state) operation under control of the software monitor.

FIG. 7 depicts a state diagram depicting the sequencing which forces to the ON state during an activity window period under control of the software monitor.

FIG. 8 depicts a representation of operation for a spreadsheet application program.

FIG. 9 depicts a representation of operation for a word-processing application program.

FIG. 10 depicts a representation of operation for a windowing application program.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Computer System—FIG. 1

In FIG. 1, computer 3 is typically a small, battery-powered computer such as a “notebook” computer. The computer 3 includes a CPU 4, a CPU bus 5, a plurality of I/O controllers 6-0, . . . , 6-n where “n” is a constant equal, for example, to 7. Connected to the controllers 6-0 through 6-n are plurality of peripheral devices 7-0, . . . , 7-n, respectively. The controllers and peripheral devices 6 and 7 typically include a keyboard, a display, a hard disk drive, a modem, a printer, and similar devices. Each of the controllers 6-0 through 6-n connects to the conventional computer bus 5.

Also connected to the bus 5 is the memory, which in one particular embodiment is DRAM random access memory 11. The memory 11, when of the type requiring refresh, is refreshed with *RAS and *CAS lines 29 under control of the PC controller 13 which provides *PCRAS and *PCCAS signals on lines 30 to power management unit 15 including a hardware monitor 79 and a software monitor 80. The I/O devices are separately powered through switch unit 22 and switches 22-0, . . . , 22-n by the VCC power from power supply 9 which receives power either from the battery 10 or an AC source 14. Power supply 9 is of a conventional type which supplies a low battery signal LB, a low-low battery signal LLB, and an AC power signal ACPWR to power management unit 15.

The computer 3 typically includes as software an operating system adapted to control the computer system and to control operations during application program execution. Computer 3 functions to execute application programs such as word processing, spreadsheet and data base management programs. Computer 3, during the execution of application programs, is under control of a software operating system. The operating system manages the different system parts and resources including the I/O devices 6 and 7. For example, during the execution of an application program when the CPU wishes to check to determine if any key has been depressed on a keyboard I/O device, the CPU 4 through a subroutine call to the operating system requests the operating system to execute a subroutine to perform a key-actuation detection task. Since the operating system performs many similar calls to the operating system, these calls represent detailed information about many activities within the computer system.

In FIG. 1, the computer 3, through the CPU 4, issues control and address signals on the bus 5 which define the overall computer address range for computers including the sets of address ranges for all of the memory, I/O and other devices connected to the bus 5. Whenever any of the peripherals 7-0 to 7-n are to be accessed for data to be transferred over the bus 5, the address of the corresponding I/O controller 6-0 to 6-n (either by unique address lines or unique address lines in combination with control lines) specifies the addressed one of the I/O controllers 6 and corresponding peripheral 7.

Similarly, memory 11 has locations addressed by a set of addresses on bus 5 within a memory address range. Some of the addresses in the range of addresses for memory 11 are typically allocated and reserved only as a set of video memory addresses. Whenever the video memory region 8 of memory 11 is to be addressed, address appears on bus 5 within the set of video memory addresses.

The computer system of FIG. 1 includes a power management unit 15 having a software monitor 80 and a hardware monitor 79 for monitoring activity of the computer system. The power management unit 15 is connected to the bus 5 to sense activity, using hardware monitor 79, on the bus 5 and is connected to the CPU 4 (executing the operating system and the software monitor 80), the power supply 9, the memory 11 and PC controller 13 for controlling power management.

The power management unit 15 of FIG. 1 operates to cause the computer system to enter the power conservation mode after sensing inactivity by the hardware monitor 79 or by the software monitor 80 and to enter the active mode after sensing activity or other conditions.

The hardware monitor 79 monitors the hardware to detect inactivity. The hardware monitor 79 typically is circuitry for detecting inactivity independently from the software and the software monitor 80. For example, the hardware monitor 79 senses predetermined address ranges, such as an I/O address range and a video memory address range, and monitors the activity of addresses by the CPU to addresses within these ranges. If no data transfers occur within the specified address ranges for predetermined periods of time, then a power control mode is entered to conserve power in the computer system.

The software monitor 80 monitors the activity of the operating system or other software in the system. The software monitor 80 typically is a software module linked, for example, to the operating system at boot time for monitoring subroutine calls to the operating system.

By using a software monitor 80 and a hardware monitor 79, the power management unit 15 decides exactly when to enter into power conservation mode and active mode without unnecessarily sacrificing system performance.

The power conservation mode includes a number of activity states. A first state, called a DOZE state, is entered after sensing inactivity for a first period of time by the hardware monitor or when an idle threshold is exceeded as determined by the software monitor. A second state, called a SLEEP state, is entered after sensing inactivity by the hardware monitor for a second predetermined time where the second predetermined time is greater than the first predetermined time or when the activity measurement sensed by the software monitor exceeds the idle threshold. A third state, called a SUSPEND state, is entered after sensing inactivity for a third period of time greater than the first and second time periods. Another state is OFF which turns off all power for the computer under predetermined conditions.

After having entered one or more of the activity states of the conservation mode, the power management unit switches back to the active mode when activity is sensed by the monitors.

Power Management Unit—FIG. 2

In FIG. 2, a block diagram of the power management unit 15 of FIG. 1 is shown. The power management unit includes a hardware monitor 79 (including an activity monitor 16 and a timer unit 24), a software monitor 80, a state control unit 23, a power control unit 17, a clock control unit 18, and a refresh control unit 20. The hardware monitor 79 (using activity monitor 16) analyzes the address activity on the system bus 5 to provide activity information used to control power management. The timer unit 24 times the activity information sensed by the monitor 16. The state control unit 23 controls the changes among different power consumption states to achieve power management.

The power control unit 17 controls the switches 22-0, . . . , 22-n of FIG. 1 as a function of the activity sensed by activity monitor 16 and the state determined by state control unit 23.

The clock control unit 18 controls the distribution of and/or the frequency of the CPU and other clocks as a function of the activity sensed by the activity monitor 16 and the state determined by state control unit 23.

The refresh control unit 20 controls the refresh of the RAM memory 11 of FIG. 1 at a rate which is determined by the activity sensed by the activity monitor 16 and state control unit 23.

The power management unit (PMU) 15 is provided to manage power and reduce, over time, the overall power consumption of computer 3. This management is accomplished using an activity monitor 16 to detect periods of system inactivity. During periods of inactivity, power consumption is reduced by reducing clock speeds or removing clocks through clock control unit 18, and/or by removing power through power control unit 17, and/or by controlling the refresh frequency through refresh control unit 20. Standard and slow refresh DRAM support is provided by refresh control unit 20. Inputs are provided to the power management unit 15 which will allow power on or off commands from external sources such as a pushbutton, modem ring indicator, or read-time-clock (RTC) time of day alarm.

Hardware Monitor Generally—FIG. 3

Referring to FIG. 3, the power management unit (PMU) 15 includes the hardware monitor 79 (activity monitor 16 and timer unit 24) which is designed to operate with minimal system requirements and without software support. Power management occurs in response to the hardware monitor independently of any operating system (DOS) or application program support.

In FIG. 3, the PMU 15 has its own power-on reset signal (*RESET) which is produced by a VCC power detector 71, separate from any other reset signal of computer 3, and upon initial power-on, the registers of the power management unit 15 are initialized to preestablished default values to provide basic functionality without need of any software.

While the hardware monitor 79 and the power management unit 15 are provided FIG. 3 as a hardware embodiment, a software embodiment of the hardware monitor 79 is described in the program listing of TABLE 1. Using the program listing of TABLE 1 executing in the CPU 4, power management, using a software embodiment of a hardware monitor, occurs under program control.

In accordance with the operation of the hardware monitor 79, a predetermined set of address ranges on bus 5 is monitored by power management unit 15 as part of the power management operation. For example, the predetermined set of address ranges monitored for power management typically includes all of the I/O address range, that is, the addresses of the I/O controllers 6-0 through 6-n and the video memory address range for the video memory locations 8 within the memory 11. Of course, other address ranges can be added to or used as the predetermined set for power management. The set of address ranges including the video memory and the I/O address ranges has been found to provide excellent information for controlling power management.

The hardware monitor 79 senses the activity of addresses on the bus 5. Whenever addresses within the predetermined set of addresses are not present on the bus 5 for predetermined time periods, the power management unit 15 responsively switches power consumption states and controls the consumption of power by different parts of the computer 3.

The power management unit 15 has four main operating states, namely, ON, DOZE, SLEEP, and SUSPEND, and a fifth state which is OFF. The five power management states, under control of the hardware monitor 79, are shown by the state diagram of FIG. 4. The activity monitor 16, external inputs (EXT, RESET), and the timeouts of timer unit 24 generally control the transitions between states in the state control unit 23 as shown in the state diagram of FIG. 4. The CPU 4 of FIG. 1 may also command the PMU 15 to enter any state. The commands from the CPU 4 typically derive from execution of the software monitor 80, but may derive from other CPU 4 commands.

In FIG. 3, each of the four active states (not OFF) has an associated PWR register which indicates in one embodiment which of eight power control outputs VP[0 . . . 7] on lines 33 will be active during the state. More generally, any number, (n+1), outputs VP[0 . . . n] can be employed. The PWR registers in power control unit 17 are PWRON register 57, PWRDOZE register 58, PWRSLEEP register 59 and PWRSUSPEND register 60 as shown in FIG. 3. A power control multiplexer 76 selects the eight outputs from one of the registers 57 through 60 corresponding to the current state on STATE lines 34 from unit 23, and these eight outputs drive the VP[0 . . . 7] power control outputs from EXOR unit 35. Also, the CPU 4 of FIG. 1 can write, under program control, to any of the PWR registers 57 through 60 to control which of the I/O devices 6 and 7 are powered at any time.

To turn an I/O device on, the corresponding bits in the PWR registers 57 through 60 for the state(s) in which they are to be on is typically high. The POLARITY register 61 specifies the actual polarity of each output VP[0 . . . 7] required to turn the associated one of the switches 22-0, . . . , 22-n on and thereby supply power to the I/O devices 6 and 7. The default value of the POLARITY register is 03h, which implies a logic low to turn on VP[2 . . . 7], which will typically control logic switches 22 with low-true output enables (for example, switches 22 typically include a PNP transistor in the VCC line from power supply 9) and high to turn on the LCD, VP[0], and EL backlight, VP[1], power. The value of the VP[0 . . . 7] bits just prior to the polarity control by EXOR 35 may be read back through the OUTPUT register 62 to CPU 4 over bus 5.

The system clock oscillator signal CLKI is connected to the CPU Clock Control block 49 to produce the CLKOUT. From there CLKOUT, as controlled by PMU 15 and control block 49, drives CPU 4. The CLKOUT clock can be stopped for static CPU's, or reduced automatically by a divisor specified in the CLOCK field of control register 53 during DOZE and SLEEP states. CLKI is passed through unchanged to CLKOUT in SUSPEND state.

Detailed implementations of the various monitor, control and logic blocks of FIG. 3 will be clear from the following detailed description. Additionally, a software embodiment of the hardware monitor 79 including logic and control functions equivalent to those in the hardware embodiment appears as the Program Listing of TABLE 1.

Software Monitor Generally

The software monitor 80 of FIG. 2 includes a power management software module linked into the operating system, for example, during boot up time. One embodiment of the module appears as the program listing of TABLE 2.

The software monitor 80 monitors all the function calls to the operating system. Every time an idle function call is made, the activity measurement, AC(t), is incremented and then checked against thresholds. The incrementing is algebraic by the amount of D_(a), a positive DOS call number, or D_(i), a negative DOS call number.

If the activity measurement, AC(t), is below the idle threshold, T_(H), and the system is in the active mode, no action will be taken. However, if the activity measurement, AC(t), is above the idle threshold, T_(H), the power management software will check the current system status and if in the active mode, will switch to the conservation mode.

The activity measurement, AC(t), is given by the following Eq. (1): $\begin{matrix} {{\sum\limits_{a,i}\left\lfloor {^{\lceil}{{{D_{a}(t)} + {D_{i}(t)}} = {A\quad {C(t)}}}} \right\rfloor^{\rceil}}} & {{Eq}.\quad (1)} \end{matrix}$

where,

D_(a)(t)=Active DOS call numbers as a function of time

D_(i)(t)=Idle DOS call numbers as a function of time

AC(t)=Accumulated Activity Count of DOS call numbers as a function of time, that is, activity measurement

While all of the interrupts of the operating system may be assigned a D_(a) or D_(i) value the following, for example in the following CHART 1.

CHART 1 INTERRUPT CALL NUMBER TYPE I16 (keyboard poll) +12 Di I10 (video active) −25 Da I8 (timer) −25 Da I14 (communications) −400 Da

Using the values in CHART 1, each time an interrupt 16 (I16) occurs, the software monitor increments AC(t) by +12 and each time I10 or I8 occurs the software monitor increments AC(t) by −25. The value of AC(t) is shown for one example of operation in FIG. 5.

Referring to FIG. 5, the value of AC(t) as a function of t is shown. In the example of FIG. 5, the first eight values of t find keyboard polling occurring by the I16 interrupt so that +12 is added to AC(t) for each of the first eight values of t. In FIG. 5, at t=8, the timer interrupt I8 occurs and subtracts −25 from the AC(t) value. Thereafter the keyboard polling continues until the value of AC(t) reaches 128, the value of T_(H) in the example of FIG. 5. At t=12 in FIG. 5, AC(t) is reset, for example, to 0 when the computer system enters the conservation (idle) mode. At about t=20 in FIG. 5, which may include a long time duration generally indicated by the broken line at about t=15, video interrupt I10 becomes active and starts to add −25 to the AC(t) value until at about time t=35 the value of AC(t) reaches the −256 value of the threshold T_(L).

When the value of AC(t) is above T_(H), then the software monitor is operative to switch the computer system into the conservation mode. Whenever AC(t) is in below the threshold T_(L), the software monitor is operative to switch the computer system back to the active mode.

The example of FIG. 5 is only for purposes of representing the manner in which AC(t) is incremented as a function of the positive and negative interrupt call numbers. Of course, other counting methods may be employed. In the program of TABLE 2, after the T_(H) value of +128 is reached, the counter is reset to +256 and each value of Da decrements the count until the threshold TL is reached at 0.

The operation which occurs when the value of AC(t) exceeds the threshold T_(H), is explained with respect to the flowchart of FIG. 6.

In FIG. 6, the value of D (either Da or Di), the interrupt number value, is added as indicated in Eq. (1) to form the accumulation value of the activity measurement, AC(t). This accumulation is indicated by the oval marked D in FIG. 6.

Next, the value of AC(t) is compared with the threshold T_(H). If the value of the summation in Eq. (1) is not greater than the threshold, T_(H), then the N no choice is made the loop repeats so that the next value of D is added to the AC(t) activity measurement. For example, in FIG. 5, this activity continues until approximately t=12 in FIG. 5.

In FIG. 5, at about t=12, the activity measurement AC(t) equals or exceeds the threshold T_(H) and hence the Y output of the comparison connects to the SLEEP state detector. If already in the state, then the Y output will force the computer system to remain in the SLEEP state. If not in the SLEEP state, then the software monitor will force the computer system into the DOZE state.

Note that the FIG. 6 operation will force the computer system into the DOZE or SLEEP state as long as the activity measurement AC(t) exceeds the threshold T_(H). When the threshold T_(H) has been exceeded, AC(t) is reset and remains reset until another activity event, Da or Di, occurs. In FIG. 5, for example, this occurs at about t=20 when AC(t) begins to count toward T_(L).

In addition to the comparison of the activity measurement AC(t) against the upper threshold T_(H), the software monitor 80 also compares the value of the activity measurement against the lower threshold T_(L). This comparison is represented by the flowchart of FIG. 7.

In FIG. 7, the oval represents the incrementing of the activity measurement AC(t) in accordance with Eq. (1). After each incrementing of the activity measurement, the value of AC(t) is compared to determine if it is less than or equal to T_(L). If not, then the N output of the comparison continues the incrementing of the activity measurement for each new value determined in accordance with Eq. (1).

If the activity measurement AC(t) is less than or equal to T_(L), then the Y output of the comparison connects the operation to the activity window comparison.

If AC(t)≦T_(L) and AW(t)≦T_(aw), then the FIG. 7 operation switches to the ON state.

If AC(t)≧T_(H), then test sleep state.

where,

T_(H)≧K₁

T_(L)≦K₂

T_(H)=Idle Threshold

T_(L)=Activity Threshold

K₁=128

K₂=−256

Combined Hardware Monitor and Software Monitor Operation

If the system is in ON state and AC(t) is greater than or equal to T_(H), the power management software monitor will bring the system into DOZE state. If the system is already in DOZE or SLEEP state, no further action will be needed. Similarly, the activity count, AC(t), will be decremented every time an active function call, Da, is made. The activity count is then used to compare with the active threshold. If the count is higher than the active threshold, T_(H), then the power management software monitor 80 will force the system into the power conservation mode (DOZE or SLEEP) per the FIG. 6 operation regardless of the status of the hardware monitor 79. If the activity count is equal to or less than the active threshold, T_(L), then the system will be programmed into the ON state.

The ON state can also be entered if the hardware monitor 79 detects a predetermined set of address ranges on bus 5. For example, the predetermined set of address ranges monitored for power management typically includes all of the I/O address range, that is, the addresses of the I/O controllers 6-0 through 6-n, and the video memory address range for the video memory locations 8 with the memory 11. Of course, other address ranges can be added to or used as the predetermined set for power management. The set of address ranges including the video memory and the I/O address range has been found to provide excellent information for controlling power management.

After entering the ON state, the power management unit will continue to be in the ON state until any idle function call detects the activity count has reached or gone beyond the idle threshold, T_(H).

There are application programs such as Microsoft's Windows described in connection with FIG. 10 that do not use the DOS idle function calls and therefore the system would never go into the DOZE state through operation of the software monitor 80. Therefore, a watch dog timer is built into the power management software monitor to monitor the absence of idle function calls as indicated in connection with FIG. 7. If a time period greater than T_(aw) as shown in the flow chart in FIG. 7 has been exceeded without any idle function call being made, then it is assumed that the application program bypasses DOS and goes directly to the hardware.

During the T_(aw) time period (see FIG. 7) the power management unit will be forced into the ON state until detection of activity for predetermined period of time, T_(aw). This period, T_(aw) is normally more than a minute in order not to affect the system performance. There is no power saving during the time out period, T_(aw), even if the CPU is actually idling. After the T_(aw) time period, the hardware monitor 79 will take over completely.

In most cases, application programs go through DOS to perform I/O operations. The power management software monitor 80 keeps track of all the operating system function calls. If the accumulative count of all active and idle function calls is greater than the upper threshold, T_(H), then the system is assumed to be inactive. The power management software monitor will program the power management unit to DOZE state only if the system is still in ON state. The computer 3 will enter DOZE state without waiting for the ON state timer to expire and therefore maximizes the power saving of the system. If computer 3 is already in DOZE or SLEEP, no action will be needed from the power management software monitor until the system becomes active again.

In the software monitor 80, inactivity is determined by detecting how many active or idle function calls an application makes within some time period. In the IBM PC DOS environment, the activity status is checked no less frequently than every 50 milliseconds. There are 256 IBM PC DOS function calls and each is labeled as idle or active with a corresponding positive or negative number. A positive number is assigned to an active function call and a negative number to an idle function call. The power management software module keeps a running total of the accumulated value of the function call numbers as the function calls are made. Whenever a function call is made, (either active or idle), the power management software module algebraically adds the number to the accumulated value and decides whether the system is active or not by comparing the magnitude of the accumulated value with a function call threshold. The function call threshold for determining activity is a variable depending on the computer system speed.

To prevent the system from oscillating between the active and idle state due to minor changes in system activity, hysterisis is provided by using active, T_(L), and idle, T_(H), function call thresholds. The accumulated total is clamped at T_(H) after it reaches the active thresholds T_(H) or T_(L) as the case may be. The active and idle thresholds are typically unequal (128 and −256) so that the entry and exit from conservation (idle) mode is biased. For example, in order to have the system enter the idle mode quickly and thereby to reduce power consumption, the active threshold is set with a threshold number (128) greater than the idle threshold number (−256). Also, functions that require immediate attention are assigned numbers large relative to the active and idle thresholds so that a single occurrence of the function call (for example, I14=−400) will force the accumulated count over the active threshold (T_(L)=−256) and thus force the system to be in the active mode. The hysterisis effect can be bypassed by forcing the power management unit into active mode without changing the activity count. In this case, the next idle function call will bring the system back to idle mode.

If the software monitor 80 or the hardware monitor 79 indicates inactivity, the power management unit enters the conservation mode which has multiple states with different levels of power conservation.

The hardware monitor 79 works in conjunction with the software monitor 80 linked to the operating system during boot up time. The state control unit 23 is controlled by the timer unit 24 and power management software module 100. The power management software will override the hardware timer unit 24 whenever inactivity is detected in the operating system level. Since this can be done in a much finer resolution than the hardware monitor 79, the combined software and hardware monitor maximize power saving without any degradation in system performance.

Power Management Unit Detail—FIG. 3

Line List

In FIG. 3, the following lines and functions are defined for the connections output (O) from and input

Name Type Function SA[0..9] I System Address on bus 5 SD[0..7] I/O System Data on bus 5 VP0 O LCD power control VP1 O EL backlight power control VP[2..7] O Peripheral power control *RAS O *RAS for DRAM *CAS O *CAS for DRAM *PCRAS I *RAS for DRAM *PCCAS I *CAS for DRAM *VCS I Video RAM chip select *IOR I I/O Read *IOW I I/O Write *S1 I Status, low indicates read or mem read operation AEN I DMA enable INMI I NMI input from user system NMI O NMI output to CPU INTR I Int request output of computer DRQ[0..3] I DMA requests which could occur in DOZE or SLEEP *DACK0 I Indicates refresh DMA cycle EXT I External command input (button) RI I Ring indicator from modem RTC I Alarm output from RTC CLKI I CPU clock input CLKOUT O Clock out to CPU LB I Low battery detect, first warning LLB I Low battery detect, second warning ACPWR I AC power good input *RESET I External RC required for reset *REFRSEL O Low when PMU controls DRAM refresh OSC I Xtal osc output CLK1IN I Clock 1 in for switched clock 1 out CLK1OUT O Switched clock 1 out CLK2IN I Clock 2 in for switched clock 2 out CLK2OUT O Switched clock 2 out LBPOL I Low battery polarity select STATIC_CPU I Connect to Vcc if CPU is static VCC Power VSS Ground

Registers

In FIG. 3, the PMU 15 includes a number of registers accessed for read or write by CPU 4 over bus 5 via an index register addressing scheme. When not accessed by CPU 4, for example, after a power on detection by detector 71, the registers are all initialized to a default state. When accessed by CPU 4, an index value is first written to the index register 50 from bus 5 and the index value is decoded by decoder 70 to select one of the registers of PMU 15 for access to bus 5 to receive or send information from or to CPU 4. The index register 50, after an index write, is changed to point to another register to be accessed. When reset, the index register is not active to enable any PMU 15 register. This is a safety feature to help prevent applications executing on the CPU 4 from inadvertently accessing PMU 15 registers. All registers may be read and written over bus 5.

Data Register (Ref. No.-FIG. 3) Index Decode STATUS 51 00H SUPPLY 52 02H CONTROL 53 04H ACTMASK 54 06H NMIMASK 55 08H OSC 56 0AH PWRON 57 0CH PWRDOZE 58 0EH PWRSLEEP 59 10H PWRSUSPEND 60 12H POLARITY 61 14H OUTPUT 62 16H DOZE 63 18H SLEEP 64 1AH SUSPEND 65 1CH LCD 66 1EH EL 67 20H

Status Register Bit Name Function D7 RESUME Resuming from SUSPEND (warm start) D6 WU1 Wakeup code MSB D5 WU0 Wakeup code LSB D4 NMI2 \ D3 NMI1 > NMI cause code D2 NMI0 / D1 STATE1 State MSB D0 STATE0 State LSB

In register 51, only D0 and D1 are affected by a write. The CPU 4 can write the state code to this register to put the PMU in another state. Writing OFFh puts it in the OFF state. The NMI cause, state and wakeup codes are decoded as follows:

Code Wakeup NMI Cause Code State Code Cause 000 None, or INMI 00 On 00 001 EXT input 01 DOZE 01 E X T input 010 LB 10 SLEEP 10 R T C input 011 LLB timeout 11 SUSPEND 11 R I input 100 SLEEP timeout 101 SUSPEND timeout

*RESET Bets STATE[0 . . . 1] and clears all other bits.

Supply Register

This register 52 is read only. D[0 . . . 2, 5] are driven directly by the input lines. Bit D3 is set when system activity is detected and is cleared when this register is read.

Bit Name Function D5 STATIC_CPU 1 = Static CPU (clock stops in DOZE) D4 DRAMRDY 1 = CPU controls DRAM (same as *REFRSEL) D3 ACTIVITY System activity present D2 LLB Low battery 2 (second warning) D1 LB Low battery 1 (first warning) D0 ACPWR AC power input in range

Control Register Bit Name Default Function D7 0 D6 RING2 0 \ D5 RING1 0 > Number of RI pulses required for turnon D4 RING0 1 / default = 1 D3 STATIC_CPU 0 For static CPU's D2 SLOW 0 Clock runs slow in ON D1 CCLK1 1 CPU Clock divisor, DOZE and SLEEP D0 CCLK0 0 / default divisor = 4

In register 53, the RING[0 . . . 2] bits are used to set the number of RI pulses required for turnon. The default value is 1 so that only one pulse is required for turnon. If set to 0, RI is disabled. State logic 23 has conventional logic for detecting and counting RI pulses from a modem, one of the I/O peripherals 7-0 to 7-n. D3 is only used for static CPU's. SLOW indicates reduced clock speed operation in On. The CCLK[0 . . . 1] bits select the clock divisor for CLKOUT in SLEEP and DOZE states, and in ON if SLOW is set, according to the table.

Bit Name Function Default D6 OS2 Mask INMI input 0 D5 MSK_SUSPEND Mask SUSPEND timeout 1 D4 MSK_SLEEP Mask SLEEP timeout 1 D3 MSK_LLB Mask LLB input 1 D2 MSK_LB Mask LB input 1 D1 MSK_EXT Mask EXT input 1

CCLK[0..1] Divisor 0 1 1 2 2 4 3 8

The activity monitor ACTIVITY output is the logical OR of all unmasked activity sources. This register 54 affects only the ACTIVITY output. Refresh DMA cycles (*DACK0 low), interrupts, or accesses to the PMU 15, never affect the activity monitor 16.

NMIMASK Register

This register 55 masks the various NMI sources. In the default state only the INMI input can generate NMI.

ACTMASK Register Bit Name Default Function D7 0 D6 MSK_VIDM 0 Mask access to video memory D5 MSK_DMA 0 Mask all DMA activity D4 MSK_P63 1 Mask access to port 63h D3 MSK_PIC2 0 Mask access to port A0h1 A1h D2 MSK_RTC 1 Mask access to port 70h, 71h D1 MSK_KBD 0 Mask keyboard (port 60H, 64H) D0 MSK_IO 0 Mask access to all ports not maskable by D[2..5]

OSC Register Bit Name Default Function D7 OSCDIV3 1 \ D6 OSCDIV2 1 OSC input divisor −1 D5 OSCDIV1 0 default code = 1101 (divisor=14) D4 OSCDIV0 1 / D3 D2 SLWREF 0 Slow refresh DRAM D1 RASWIDTH1 0 *RAS pulse width MSB D0 RASWIDTH0 0 *RAS pulse width LSB

Referring to register 56, OSCDIV[0 . . . 3] plus one is the OSC frequency in MHz, except for OSCDIV[0 . . . 3]=13, the default, indicates 14.318 MHz. SLWREF is set when slow refresh DRAM is used. RASWIDTH[0 . . . 1] indicates the width of the *RAS pulse in units of OSC periods. The default value is 0 which disables refresh in SUSPEND state, and no RAS/CAS is generated. Values of 1 to 3 indicate 1 to 3 OSC periods.

PWR Registers

The bits D[0 . . . 7] in these registers 57 through 60 correspond directly with the power control outputs VP[0 . . . 7]. In a particular state, the corresponding PWR register outputs control the VP lines 23. The exception is VP0 and VP1 which are LCD and EL power, respectively. These outputs are AND'ed in AND gates 41 and 42 with the LCD and EL timer outputs prior to driving the lines 33. All bits are then exclusive NOR'ed in gates 35 with the POLARITY register 61, and the result drives the lines 33. The default values for these registers are as follows, where 1 indicates that the controlled device is on:

PWRON FFh PWRDOZE FFh PWRSLEEP 0Fh PWRSUSPEND 00h

POLARITY Register

This register 61 controls the polarity of the VP outputs. If a logic low is required on a VP line to turn the external device on, the corresponding bit in the POLARITY register 61 must be low. If a high is required, set the bit high.

Timer Registers

The nonzero value loaded into one of the timer registers 63 through 68 is the actual timeout minus one. A zero disables the timeout. Therefore a 4 bit timer can be set for a timeout from 1 to 15 time units. Reading a timer register returns the value that was last written to it, not the actual time remaining. The default values are tabulated below:

Timer Range Default DOZE 1-15 sec 5 sec SLEEP 1-15 min 2 min SUSPEND 5-75 min 0 (disabled) LCD 1-15 min TBD EL 1-15 min TBD

OUTPUT Register

The OUTPUT register 62 is a read only register. For each VP[0 . . . 7] output that is on, the corresponding bit in the OUTPUT register will be set.

The control and logic functions for the activity monitor 16, the state logic 23, the NMI logic 21, and other components of FIG. 3 are conventional logic circuits for implementing the logic and control functions hereinafter described or alternatively are the software logic of TABLE 1.

ON State

Referring to FIG. 4, the ON state is entered from the SUSPEND or OFF state when the *RESET input is low, and also when one of EXT, RTC or RI goes high if ACPWR is true or LB is false. It is entered from DOZE or SLEEP when the activity monitor 16 detects activity with addresses in the predetermined address set. In the ON state encoded on lines 34, all power control outputs VP[0 . . . n] will be controlled by the PWRON register 57. Upon entering the ON state, the DOZE timeout timer 63 will be retriggered. The LCD and EL timeouts in timers 66 and 67 will be retriggered when entering the ON state from SUSPEND or OFF. The retrigger lines from STATE logic 23 to the timers are not shown in FIG. 3 for clarity.

In FIG. 3, the STATE logic 23 recieves the CPU data bus D(0 . . . 7) from bus 5 for receiving state commands issued by the software monitor 80 of TABLE 2. The STATE logic also receives the address detection line 76 from activity monitor 16 which enables the STATE logic 23 to receive the state commands from the software monitor when addressed over the bus 5.

If the SLOW bit in the control register 53 is false, the CLKOUT rate on line 28 will be full speed. If the SLOW bit is true, CLKOUT will be as specified by the CCLK[0,1] bits in register 53. This clock control allows the user to save power, for example, when running non-computationally intensive applications such as word processing.

DOZE State

The DOZE state is entered from the ON state when the activity monitor 16 has not detected activity and therefore has not provided the ACTIVITY signal within the time, T1, specified by the DOZE timer 63. In the DOZE state encoded on lines 34, the power control outputs VP[0 . . . 7] from unit 17 are controlled by the PWRDOZE register 58. If a non-static CPU 4 is used, the clock on line 28 will be slowed as specified by CCLK[0,1] in register 53.

If a static CPU 4 is used, CLKOUT on line 28 will stop in the low state immediately following a non-DMA memory read instruction, as indicated by *S1 going high while *AEN is low, so that no chip select will be low. If INTR goes high, CLKOUT will be enabled until after EOI is written to the interrupt controller with INTR false. If INMI goes high, CLKOUT will be enabled. If an internally generated NMI occurs, CLKOUT will be enabled until the NMIMASK register 55 is read. If any DRQ goes high, CLKOUT will be enabled until after the next memory read instruction with AEN and all DRQ inputs false. The enable request functions for INTR, INMI, internal NMI and DMA are separate and CLKOUT is enabled when any event requests it, so that an interrupt handler in CPU 4 will run to completion even if it is interrupted by a DMA request. These enable request functions are independent of the activity monitor and the ACTMASK register 54. Enabling CLKOUT does not cause the PMU 15 to leave DOZE, unless the activity monitor 16 is subsequently triggered. If this trigger occurs, the PMU 15 will enter the ON state and the enable request logic will be cleared.

SLEEP State

The SLEEP state is entered when the PMU 15 has been in the DOZE state for the time, T2, specified by the SLEEP timer 64 and no ACTIVITY signal has occurred. In the SLEEP state, the CLKOUT operation is the same as in DOZE. The power control outputs are controlled by the PWRSLEEP register 59.

Alternatively, the PMU can be programmed to generate NMI and remain in DOZE state instead of automatically entering SLEEP.

SUSPEND State

The SUSPEND state is entered when the PMU 15 has been in the SLEEP state for the time, T3, specified by the SUSPEND timer 65 or when a power check detects low battery signals, LB or LLB. The SUSPEND state is entered after these conditions only when the CPU 4 writes the code for SUSPEND to the STATUS register 40 and this operation requires software support because in SUSPEND the CPU operation is affected. In SUSPEND operation, CLKOUT is the same as CLKI. The power control outputs are controlled by the PWRSUSPEND register 60. In SUSPEND, the CPU 4 and the device (for example, a switch) which generates the system reset signal must be powered off. Only activity on the EXT, RI or RTC inputs can cause an exit from SUSPEND, and the new state after exit will be ON. When the reset circuit power is restored, it will reset the CPU 4, which will then execute a warm startup routine in a conventional manner. DRAM refresh may be enabled in SUSPEND. If DRAM refresh is not enabled, the PMU 15 does not need OSC from unit 43 in SUSPEND, and gates it off internally to minimize OSC power consumption. The OSC output will stay low. The bus interface is inhibited, and the data bus 5 is tristated.

OFF State

The OFF state is entered when the CPU 4 writes the code of OFF (OFFh) to the STATUS register 51. It is also entered 5 seconds after the EXT input goes high if the NMI is not serviced.

The OFF state is meaningful only when the PMU 15 is powered from a battery while the rest of the computer 3 is turned off. This type of power connection is necessary only if the PMU 15 must awaken the system from the OFF state by activating VP outputs on lines 33 in response to transitions on the EXT input. If this function is not required, then the PMU 15 may be powered off when the system is powered off, and the OFF state as described below is not required.

In the OFF state, all outputs from the PMU 15 are either low or tristated, and all devices other than PMU 15 in the computer 3 are powered off. Any inputs will have pulldowns so that floating inputs, if any, will not cause increased power dissipation. Only activity on the EXT, RI or RTC inputs can cause an exit from OFF, and the new state will be ON. The bus 5 interface is inhibited and data bus 5 is tristated.

Activity Monitor

The activity monitor 16 includes an address detector 73 which receives addresses from bus 5 representing the address activity of the CPU 4. The address detector 73 receives, for example, control lines and address lines SA(0 . . . 9) from bus 5 for sensing when those addresses are within the predetermined address set. The predetermined address set is defined, for example, by an address set specified by ACTMASK register 54. The detector 73 compares or masks the address set specified by register 74 with the addresses on bus 5 and provides an address detect signal on line 76 to the logic 77. The logic 77 receives the other inputs to the activity monitor 16 and combines them, using conventional logic circuitry, to provide three outputs.

The three outputs provided by activity monitor 16 are produced by conventional logic or by software as shown in TABLE 1. The EXTRIG output is a function of keyboard activity only and is used to retrigger the EL backlight timer 67. The LCDTRIG output is true for keyboard activity or video memory writes, and retriggers the LCD timer 66. The ACTIVITY output is an OR function of a programmable selection of different activities specified in the ACTMASK register 54. When active, this output returns the PMU 15 to the ON state and retriggers the DOZE timeout timer 63. The activity monitor 16 does not produce the ACTIVITY output in response to accesses to the registers of PMU 15.

OSC Programmability

The OSC frequency of refresh control unit 20 provides the timebase for the timers and the refresh for DRAM memory 11. The PMU 15 may be programmed to accept a range of OSC frequencies. The OSC frequency of oscillator 43 is fed to a counter 44 which divides it by a divisor which is programmed in the OSC register 56. The programmable counter output of divider 44 is divided to produce 256 Hz which is used by the refresh control logic 48. Further dividing in divider 46 produces 32 Hz for slow refresh to refresh control logic 48, and 8 Hz and 1/(7.5) Hz for use by the timers 63, 64, 65 and 68.

Timers

There are six timers in the PMU 15, namely, DOZE timer 63, SLEEP timer 64, LB (low battery) timer 68, SUSPEND timer 65, EL (backlight) timer 66, and LCD timer 67. Each of the six timers a 4-bit register loadable by CPU 4 over bus 5. Setting a timer register to 0 disables it; setting it to a nonzero value enables it. If enabled, certain timers are triggered by the transition to the ON state. Individual timers are also triggered by events specific to their functions. Some timers are retriggerable, timing out at a programmable time following the last trigger.

The DOZE timer 63 is programmable from 1 to 15 seconds with a resolution of 1 second, and the SUSPEND timer 65 is programmable from 5 to 75 minutes with a resolution of 5 minutes. All other timers are programmable from 1 to 15 minutes with a resolution of one minute. There is a quantization error associated with retriggering any timer. This error is a quantization error associated with retriggering any timer. This error will cause the actual timeout to be up to ⅛ of the resolution of the timer longer (but never shorter) than the programmed value. The error does not vary with the programmed value.

The LCD timer 66 and the EL timer 67 are retriggerable. The timer outputs are AND'ed in AND gates 41 and 42 with the power control bits selected by the power control multiplexer 76 according to the current PMU state to control the LCD (VP0) and EL (VP1) power control outputs to EXOR 35. This operation provides the flexibility to turn the EL and LCD outputs off when the associated timers 66 and 67 time out, or to control the outputs in any PMU power-management state under control of multiplexer 76.

The DOZE timer 63 is retriggerable and is triggered by the activity monitor ACTIVITY output in the ON state, and triggers the transition to DOZE state when it times out.

The SLEEP timer 64 is triggered when the DOZE state is entered and is cleared when the DOZE state is exited. Timer 64 either generates NMI or triggers the transition to SLEEP state when it times out.

The SUSPEND timer 65 is triggered when the SLEEP state is entered and is cleared when SLEEP is exited. If unmasked, an NMI will be generated when it times out.

The LB timer 68 is enabled when ACPWR is false (no AC power). Timer 68 is triggered when LB is first detected. If unmasked, NMI is generated by the LB timer 68 output once per minute when it times out, until a period of one minute elapses during which LB remains continuously false. The NMI cause will be identified as an LB or LLB interrupt. Software can maintain a counter and display a message once per X interrupts. It can also monitor LLB and shut the computer down after Y interrupts. It can also monitor LLB and shut the computer down after Y interrupts with LLB true.

NMI

The PMU unit 15 OR's together a number of internally generated NMI requests to produce the NMI output on line 27. These requests can be masked by bits in the NMIMASK register 55. The INMI input comes from conventional external NMI-generating logic such as a parity detector, and can be OR'ed with the internal NMI requests to generate NMI when unmasked by the OS2 bit in the NMIMASK register 55. The NMI output on line 27 generally goes to the CPU NMI input, except on OS2 systems where it must go to an IRQ. The NMI CAUSE code bits in the Status register 40 indicate the cause of the NMI on line 27. An internally generated NMI is cleared by reading the NMIMASK register 55.

NMI may be generated to indicate a low battery when ACPWR is false.

If the MSKSLEEP bit is cleared, the PMU 15 will generate NMI when the SLEEP timer 64 times out and remain in DOZE instead of entering SLEEP.

NMI is also generated when the SUSPEND timer 65 times out. Software can then save status and go to SUSPEND or OFF state.

A high on the EXT input while not in the OFF or SUSPEND state will generate NMI. Software can then save status and go to SUSPEND or OFF state. If the NMI is not serviced within 5 seconds, the PMU 15 assumes there is no software support for SUSPEND and will turn all power off and enter the OFF state.

Refresh in SUSPEND State

Refresh is enabled by setting the RASWIDTH[0 . . . 1] bits in the OSC register 56 to a nonzero value. This enables OSC to run in SUSPEND mode, and the RASWIDTH value also sets the width of the *RAS pulse in units of OSC clock periods. Slow refresh is enabled by setting SLWREF high. The PMU 15 generates *MRAS and *MCAS signals to mux 32 to refresh DRAM while the CPU is powered off or being reset. When the CPU is active, the *PCRAS, *PCCAS signals on lines 30 from the PC controller 13 are selected by multiplexer 30 to provide the *RAS, *CAS signals on lines 29. *REFRSEL on line 72 will go low to indicate that the PMU 15 is controlling refresh and high for PC controller 13 control.

If enabled, the DRAM refresh outputs are active in SUSPEND. When entering SUSPEND, the PMU 15 immediately generates a burst of 1024 CAS before RAS refresh cycles. A burst of 256 cycles is then repeated every 3.9 ms if SLOWREF is false or every 31.25 ms if SLOWREF is true. After entering the ON state from SUSPEND, the PMU 15 generates bursts of 1024 refresh cycles over 2.9 ms. This operation allows as much time as needed for CPU power stabilization, crystal oscillator startup and CPU reset. When the CPU is ready to take over control of the DRAM, it must poll the SUPPLY register 38 until the DRAMRDY bit goes high. The PMU 15 senses the polling operation as a request from the CPU for DRAM control, and at the end of the first refresh burst following a CPU I/O read of the SUPPLY register 38, the PMU 15 sets *REFRSEL high to return control of the DRAM to the CPU. The DRAMRDY bit is essentially the same signal as *REFRSEL.

The purpose of the bursts when entering and leaving SUSPEND is to eliminate violations of the refresh rate spec when switching between external refresh row address generation (DMA cycles during ON) and internal row address generation (CAS before RAS during SUSPEND).

Pseudostatic RAM refresh is also supported. When *REFRSEL goes low, *RAS can drive *RFSH low for auto refresh mode. The burst refresh will assure that switching between external and internal refresh will not violate the refresh rate spec. Self refresh can also be used by driving *RFSH low when *REFRSEL is low, but other logic will have to generate the refresh burst when entering and leaving SUSPEND, if required.

External Wakeup Inputs

RI is a rising edge sensitive input, to state logic 23 from a modem ring indicator RI output of a peripheral 7. The number of rising edges required for this input to be recognized is specified in bits D[4 . . . 6] of the Control register 53. The default is one transition. If these bits are zero, this input is disabled. If enabled, a rising transition on this input will force the PMU 15 to the ON state.

RTC is an edge sensitive wakeup-alarm input from a real time clock in CPU clock control 49 of FIG. 3. A rising or falling transition on this input will force the PMU 15 to the ON state.

EXT is a rising edge sensitive input, intended for use with an external pushbutton. A rising transition on this input while the PMU 15 is in OFF or SUSPEND will force the PMU 15 to the ON state. A transition in ON, DOZE or SLEEP will generate NMI.

EXT is debounced in ON, DOZE and SLEEP in a conventional debouncer circuit 36. A rising edge immediately generates NMI but only if EXT has been sampled low at least twice by a 32 Hz debounce clock from counter 46 prior to the rising edge. The debounce clock is derived from OSC 43 and therefore may be stopped in SUSPEND and OFF, so the PMU 15 will not enter these states until the debounce operation is completed. To prevent resuming due to contact bounce on the release of a pushbutton, the PMU 15 will defer execution of a change of state command from the CPU 4 until after the EXT input has been sampled low twice by the debounce circuit 36. This operation is typically transparent to software. For example, if the user presses the button in ON, the PMU 15 will generate NMI, and the CPU will write the command to enter SUSPEND and then execute a halt instruction. Nothing will happen until after the pushbutton is released, at which time the PMU 15 will enter SUSPEND.

Resume and Power on

The PMU 15 has its own private *RESET signal, typically from an external RC network detector 71 which detects VCC. This signal resets only the PMU 15 when power, VCC, is first applied to it. A separate reset signal must be generated by external hardware for the CPU when entering the ON state from SUSPEND or OFF state. At power on, the CPU 4 must read the RESUME bit in the Status register 51. RESUME will be cleared if the startup is a cold start from OFF and will be set to indicate a warm start (resume) from SUSPEND. If RESUME is cleared, the wakeup bits WU[0 . . . 1] in the Status register 51 will be zero, otherwise they will indicate which external input caused the resume. The RESUME bit will be cleared after the Status register is read.

Clock Switching

The clock switch control 69 is provided to switch input clocks CLK1IN and CLK2IN clocks to output clocks CLK1OUT AND CLK2OUT for peripherals. The CLK1 and CLK2 operations are the same. For example, the CLK1IN is passed to the CLK1OUT output by control 69 in ON and DOZE. When entering SLEEP mode, CLK1OUT will stop synchronously in the low state. CLK1OUT will start synchronously when returning to the ON state.

Low Battery Detection

The LB and LLB inputs indicate low battery and low low battery as generated by a conventional battery level detector in power supply 9 of FIG. 1. The polarity of these inputs is programmable by the LBPOL line which can be strapped low or high. If this line is high, LB and LLB are high true. If low, these inputs are low true. The status of the LB and LLB lines after polarity correction can be read in the SUPPLY register 38. A low battery indication can generate NMI.

Power Sequencing

To minimize turnon transients, the turnon of VP1 (EL power) is delayed by 4 to 8 ms after OSC begins clocking, when entering the ON state.

Program Listing

A computer program embodiment of the hardware monitor for the power management unit appears in the following TABLE 1.

TABLE 1 ; ================================================== ;  Power Management Software ; ================================================== ; ;   Copyright - 1989 Vadem, Inc. ; ;   All Rights Reserved. ; ;     C: ; ================================================== .xlist include romeq.dec include romdef.dec include seteq.dec include clkeq.dec include 8250eq.dec include prneq.dec include crteq.dec include vg600.dec include notes.dec include kbdeq.dec .list include pwreq.dec CMSG <Power Management BIOS Kernel> pmdata segment para public ‘pmdata’ extrn on_power_status:word extrn sleep_power_status:word extrn lb_event_handler:dword extrn lb_event_mask:word extrn doze_timeout:byte extrn doze_count:byte extrn sleep_timeout:byte extrn sleep_count:byte extrn kbd_timeout:byte extrn kbd_count:byte extrn pwr_off_timeout:word extrn pwr_off_count:word extrn led_time_on:byte extrn led_time_off:byte extrn led_next_event:byte extrn led_cycle_count:word extrn lb_def_event_type:byte extrn lb_event_rep:byte extrn lb_event_count:byte extrn sleep_save_buf:byte extrn pm_flags:byte extrn second_counter:byte extrn minute_counter:byte extrn one_shot_handler:dword extrn one shot_timer:dword extrn lb_last_event:word extrn pm_ram_chksum:word extrn pm_save_ss:word extrn pm_save_sp:word extrn pm_resume_stack:byte pmdata ends data0 segment public ‘DATA0’ extrn crt_addr:word extrn reset_flag:word data0 ends code segment  word public  ‘code’ assume cs:code, ds:pmdata public power_management ,power_management_init,power_management_enable public pm_timer_hook,pm_kbd_hook public pm_enter_sleep, read_com, write_com public write_crt_reg, read_crt_reg public suspend, resume extrn data0p:word extrn get_pm_ds:near extrn alloc_pm_ds:near extrn default_low_battery_alarm:near extrn rd_rtcw:near extrn wr_rtcw:near extrn rd_rtcb:near extrn wr_rtcb:near extrn play_song:near extrn set_ibm_timer:near extrn checksum:near extrn oem_pm_init:near extrn oem_pm_get_status:near extrn oem_pm_extensions:near extrn oem_pm_halt:near extrn oem_pm_activity?:near extrn oem_pm_reset activity:near extrn oem_pm_toggle_led:near extrn oem_pm_turn_on_peripherals:near extrn oem_pm_turn_off_peripherals:near extrn oem_pm_power_off:near extrn oem_pm_suspend:near extrn oem_pm_blank_video:near extrn oem_pm_restore_video:near extrn oem_pm_save_peripherals:near extrn oem_pm_restore_peripherals:near extrn oem_pm_save_video_state:near extrn oem_pm_restore video_state:near extrn oem_pm_kbd_activity?:near extrn oem_pm_reset_kbd_activity:near extrn oem_pm_make_power_off_noise:near extrn oem_pm_make_low_battery_noise:near extrn oem_pm_defaults:near extrn oem_pm_get_hw:near extrn oem_pm_get_nmi_handler:near es_arg equ word ptr [bp+16] ah_arg equ byte ptr [bp+15] al_arg equ byte ptr [bp+14] ax_arg equ word ptr [bp+14] cx_arg equ word ptr [bp+12] cl_arg equ byte ptr [bp+12] ch_arg equ byte ptr [bp+13] dx_arg equ word ptr [bp+10] dl_arg equ byte ptr [bp+10] dh_arg equ byte ptr [bp+11] bh_arg equ byte ptr [bp+09] bl_arg equ byte ptr [bp+08] bx_arg equ word ptr [bp+08] bp_arg equ word ptr [bp+04] si_arg equ word ptr [bp+02] di_arg equ word ptr [bp+00] page pwrmgt_fx_table   label word dw pm_get_profile ;get current profile dw pm_get_rtc_profile ;get profile in rtc dw pm_set_profile ;set active profile dw pm_set_rtc_profile ;update rtc profile dw pm_event_handler ;install evt handler dw pm_one_shot_event_handler ;install evt handler dw pm_get_pm_status ;get status dw pm_enter_sleep ;enter sleep dw oem_pm_power_off ;power off dw oem_pm_suspend ; suspend pwrmgt_fx_table_len  equ ($-pwrmgt_fx_table)/2 ; ================================================== ;  power_management_init ; ================================================== ; ;  Called to initialize the Data Structures for ;  the power management kernel. Allocate a Data Segment ;  initialize variables, install the default ;  Low Battery event handler, and call oem_pm_defaults ;  to setup any system specific hardware or default ;  settings. Does not enable the power management yet . . . power_management_init proc dbMESSAGE fTEST8+fTESTb <power_management_init> call alloc_pm_ds ;now sets ds . . . sub ax, ax mov pm_flags, al mov second_counter, 18 mov minute_counter, 60 ;init this stuff . . . mov ax,(SYS_PWR_MGT shl 8) or GET_RTC_PWR_PROFILE int TASKINT push dx ;save power off timeout mov ax,(SYS_PWR_MGT shl 8) or SET_PWR_PROFILE int TASKINT mov ah, CM_ALM_REP ;get alarm repeat call rd_rtcb mov cl, al ;input param mov ah, CM_DEF_ALM call rd_rtcb mov bl, al and bx, LBE_LB1 or LBE_LB2 ;default event type . . . pop dx ;restore pwr_off_timeout mov ax,(SYS_PWR_MGT shl 8) or INSTALL_LP_EVT_HANDLER push cs pop es mov di, offset default_low_battery_alarm int TASKINT jmp oem_pm_defaults power_management_init endp ; ================================================== ;  Start Power Management . . . ; ================================================== ; ;  After Initial Power Up Self Tests are completed, ;  power management is enabled. Do not enable until ;  it is time to boot the system. ; ; power_management_enable proc push ds call get_pm_ds ;load ds pointer or pm_flags, PM_ENABLED pop ds ret power_management_enable endp ; ================================================== ;  Power Management dispatch routine ; ================================================== ; ;  Programmatic interface to the Power Management Kernel. ;  used to read /alter management parameters. ; ;  This function is installed as Int 15h (task management) ;  function OCFh. Power_Management proc near sti cmp al, PM_OEM_FX ;extended function?? jnz @F ;no . . . jmp oem_pm_extensions ;do private functions @@: cmp  al,pwrmgt_fx_table_len jae md err ;not here push ds push es pusha mov bp,sp ;stack addressing . . . call get_pm_ds ;load ds pointer sub ah,ah shl ax,1 mov si,ax call pwrmgt_fx_table[si] ;execute the function popa pop es pop ds retf 2 ;return md_err: mov ah,86h ;fx err stc retf 2 ;save flags Power_Management endp page ; ================================================== ;  pm_get_profile ; ================================================== ; ;  Return to caller the current active profile. ;  This may have been modified by Set profile calls. ; pm_get_profile: dbMESSAGE fTEST8 + fTESTb <pm_get_profile> mov ax,on_power_status mov si_arg, ax mov ax,sleep_power_status mov di_arg, ax mov al,lb_def_event_type mov bl_arg, al mov al,kbd_timeout mov bh_arg, al mov al,doze_timeout mov cl_arg, al mov al,sleep_timeout mov ch_arg, al mov ax,pwr_off_timeout mov dx_arg, ax clc ret ; ================================================== ;  pm_set_profile ; ================================================== ; ; Set_the current active profile. ; Alter the desired parameters. Do this by ;calling ; get profile, and then changing just those parameters ; and then calling set profile pm_set_profile: dbMESSAGE fTEST8 + fTESTb <pm_set_profile> mov doze_timeout, cl mov sleep_timeout, ch mov lb_def_event_type, bl mov kbd_timeout, bh mov pwr_off_timeout, dx mov pwr_off_count,0 ;clear countdown mov ax, si_arg mov on_power_status, ax mov ax, di_arg mov sleep_power_status, ax mov ax, si_arg call oem_pm_turn_on_peripherals clc ret page ; ================================================== ; pm_get_rtc_profile ; ================================================== ; ; Read Back current profile stored in the NV-RAM. ; This profile is the default active at power up ; pm_get_rtc_profile: dbMESSAGE fTEST8 + fTESTb <pm_get_rtc_profile> mov ah,CM_OPCW call rd_rtcw mov si_arg, bx mov ah,CM_SPCW call rd_rtcw mov di_arg, bx mov ah,CM_DOZE call rd_rtcw mov cx_arg, bx mov ah,CM_ALM_REP call rd_rtcw mov dx_arg, bx mov ah,CM_DEF_ALM call rd_rtcw mov bx_arg, bx clc ret ; ================================================== ;  pm_set_rtc_profile ; ================================================== ;  Set the current NV-RAM profile. ;  Alter the desired parameters. Do this by calling ;  get rtc profile, and then changing just those parameters ;  and then calling set rtc profile ;  This profile will be active next hard reset . . . pm_set_rtc_profile: dbMESSAGE fTEST8 + fTESTb <pm_set_rtc_profile> mov ah, CM_OPCW mov bx, si_arg call wr_rtcw mov ah, CM_SPCW mov bx, di_arg call wr_rtcw mov ah,CM_DOZE mov bx, cx_arg call wr_rtcw mov ah,CM_ALM_REP mov bx, dx_arg call wr_rtcw mov ah,CM_DEF_ALM mov bx, bx_arg call wr_rtcw clc ret page ; ================================================== ;  pm_event_handler ; ================================================== ; ;  Install a Low Battery Event Handler. ;  Specify the Event criteria, which dictates ;  under which conditions the Event Handler is called, ;  and specify a repeat rate for recurring conditions. ;  Also specify a power off/ Suspend timeout ;  after the detection of a Low, Low Battery condition pm_event_handler: dbMESSAGE fTEST8 + fTESTb <pm_event_handler> xchg [lb_event_mask],bx mov bx_arg, bx xchg word ptr [lb_event_handler],di mov di_arg, di mov bx,es_arg xchg word ptr [lb_event_handler+2],bx mov es_arg, bx xchg [lb_event_rep], cl mov cl_arg, cl xchg [pwr_off_timeout], dx mov dx_arg, dx and [pm_flags],not PM_LB_HANDLER mov ax, word ptr [lb_event_handler] or ax, word ptr [lb_event_handler+2] jz @F or [pm_flags],PM_LB_HANDLER @@: mov  [lb_event_count], 0 ;time to do . . . clc ret ; ================================================== ;  pm_one_shot_event_handler ; ================================================== ; ;  Certain applications and/or management functions ; may wish to be notified if a timeout period occurs ; after a certain event. This function provides ; a 55 Msec resolution timing function for timing ; events, and acts like a hardware one-shot; timing out ; calling the one shot handler, and cancelling the ; timer until it is reloaded again. pm_one_shot_event_handler: dbMESSAGE fTEST8+fTESTb <pm_one_shot_handler> mov word ptr [one_shot_handler],di mov bx,es_arg mov word ptr [one_shot_handler+2],bx mov word ptr [one_shot_timer], cx mov word ptr [one_shot_timer+2], dx mov al, [pm_flags] ;get status or cx, dx ;cancel?? jz os_cancel ;yes . . . ; ==== Not a Cancel request, so check if one shot is rolling test al, PM_ONE_SHOT_HANDLER jnz os_err and al, not PM_ONE_SHOT_HANDLER mov bx, word ptr [one_shot_handler] or bx, word ptr [one_shot_handler+2] jz @F or al, PM_ONE_SHOT_HANDLER @@: mov  [pm_flags], al clc ret os_err: mov  ah_arg,86h ;already active stc ret os_cancel: and al, not PM_ONE_SHOT_HANDLER mov [pm_flags], al clc ret ; ================================================== ;  pm_get_pm_status ; ================================================== ; ;  Return the status of the System Status port. ;  this port has two defined bits: ; ;   bit 0 = Low Battery ;   bit 1 = Low, Low Battery ; ;  Other bits have OEM specific meanings pm_get_pm_status: dbMESSAGE fTEST8 +fTESTb <pm_get_pm_status> call oem_pm_get_status mov bx_arg, ax ret ; ================================================== ;  pm_enter_sleep ; ================================================== ; ;  This function sets up a sleep command at the ;  next timer interrupt ; pm_enter_sleep: or pm_flags, PM_SLEEP ;say to sleep ret assume  cs:code,ds:data0,es:pmdata ; ================================================== ;  read_crt_reg ; ================================================== ; ;  This routine is used to read the state of a ;  video register ; ; ;  inputs: bl = address in 6845 ; ;  outputs: ax = word read ; ================================================== read_crt_reg proc near mov dx,crt_addr ;set addr mov al,bl out dx,al inc dl in al,dx mov ch,al ;get msb dec dl mov al,bl ;set next addr inc al out dx,al inc dl in al,dx mov ah,ch ;get lsb ret read_crt_reg endp ; ================================================== ;  read_com ; ================================================== ; ;  This routine is used to read the status of a ;  8250 serial port and save it in memory read_com   proc ;save com port in DX add dl,lcr in al,dx or al,DLAB ;set dlab to read div reg jmp $+2 out dx,al sub dl,lcr in ax,dx ;read divisor reg stosw add dl,lcr in al,dx and al,not DLAB jmp $+2 out dx,al sub dl,lcr-ier mov cx,6 rcom1: in al,dx inc dx stosb loop rcom1 ret read_com endp ; ================================================== ;  read_lpt ; ================================================== ; ;  This routine is used to read the status of a ;  Industry Standard Parallel port and save it in memory read_lpt proc add dl,printer_control in al,dx stosb ret read_lpt endp assume cs:code,ds:pmdata,es:data0 ; ================================================== ;  write_com ; ================================================== ; ;  This routine is used to restore the status of a ;  8250 serial port from where it was saved in memory write_com proc add dl,lcr in al,dx or al,DLAB jmp $+2 out dx,al sub dl,lcr lodsw out dx,ax add dl,lcr in al,dx and al,not DLAB jmp $+2 out dx,al sub dl,lcr-ier mov cx,6 wcom1: lodsb out dx,al inc dx loop wcom1 ret write_com endp ; ================================================== ;  write_lpt ; ================================================== ; ;  This routine is used to restore the status of a ;  Industry Standard Parallel port from ;  where it was saved in memory write_lpt proc add dl,printer_control lodsb out dx,al ret write_lpt endp ; ================================================== ;  write crt register ; ;  This routine is used to restore the status of a ;  video register from memory ; ;  inputs: cx = word to write ; bl = address in 6845 ; ================================================== write_crt_reg proc near mov dx,crt_addr ;set addr mov al,bl out dx,al mov al,ch ;send msb inc dl out dx,al dec dl mov al,bl ;set next addr inc al out dx,al inc dl mov al,cl ;send lsb out dx,al ret write_crt_reg endp assume cs:code,ds:pmdata,es:nothing page ; ================================================== ;  pm_kbd_hook ; ================================================== ; ;  In Software Based Power Management, this routine ;  is part of the Keyboard Interrupt chain. It is ;  used to detect keyboard activity. ; ;  Called every KBD INT: Set Keyboard Active bit ; ;  restore video if necessary ; ;  must save regs, take care of ints . . . ; ; pm_kbd_hook: dbPC fTEST1+fTESTb “k” call get_pm_ds ;get ds test pm_flags, PM_VBLANK ;video blanked out??? jz @F ;NO call oem_pm_restore_video ;turn on screen and pm_flags, not PM_VBLANK ;clear blank flag @@: or pm_flags, PM_KBDACT ;say keyboard had activity ret page ; ================================================== ;  pm_timer_hook ; ================================================== ; ;  In Software Based Power Management, this routine ;  performs the function of the Timer and Dispatcher ;  It is part of the Timer Interrupt chain, after ;  the timer end of interrupt (EOI) has been sent. ; ;  Checks for system activity and DOZEs/ SLEEPs ; ;  Entry conditions:  cli, ds,es,pusha saved, ds=data0p ; ;  This routine contains two threads of code, ;  which execute independently. ; ; ;  COUNTER thread: ;         ; ; ;  The COUNTER thread checks for the one shot, ;  handles the second and minute counters, and looks ;  at the low battery level, and dispatches the LB ;  event handler. It then looks at the DOZE flag, ;  and if doze is active, returns without changing ;  the activity status; so that the code after the DOZE ;  HLT can function. ; ; ;  DOZE thread: ;         ; ; ;  The DOZE thread runs when an activity check ;  shows no activity has been present for the ;  entire DOZE timeout. The processor clock ;  is slowed, the DOZE bit is set, interrupts ;  are enabled, and the CPU is put into HLT. ;  When HLT is exited, (18.2 hz) the activity ;  status is checked, to see if DOZE should be ;  terminated. If activity is present, ;  the DOZE flag is cleared and the ;  activity exit is taken. ; ;  If activity is not present, a test is made ;  for the SLEEP timeout. If the SLEEP timeout ;  has elapsed, SLEEP is entered, after saving ;  the peripheral state. Otherwise, the CPU ;  is halted, and the DOZE loop is reentered, ;  and the cycle continues until ;  terminated by ACTIVITY or SLEEP. ; ; ================================================== even ,fast . . . pm_timer hook: cli ;ints are off . . . call get_pm_ds ;establish ds test pm_flags, PM_ENABLED ;running yet?? jnz @F jmp exit_wo_change ;no . . . @@: call oem_pm_get_hw ,get hw_caps to ES:DI test pm_flags, PM_ONE_SHOT_HANDLER ;have one?? jz ck_sec ;no . . . dec word ptr one_shot_timer sbb word ptr one_shot_timer,0 jnz ck_sec and pm_flags, not PM_ONE_SHOT_HANDLER ;dont any more . . . call one_shot_handler ;called w/ ints disabled ; ================================================== ;  First, handle the one second dispatching ; ================================================== even ck_sec: dec second_counter jz is_sec jmp exit_wo_change ; ================================================== ;  Second Rolled, Check Minutes ; ================================================== is_sec: mov second_counter,18 ;ticks per second . . . reset dbPC fTEST2+fTESTb “{circumflex over ( )}Q” dec minute_counter ;count minutes . . . jz @f jmp not_minute @@: dbPC fTEST2+fTESTb “(” page ; ================================================== ;  All Code Below is executed once per Minute. ;  All Minute Counters are decremented here . . . ; ================================================== mov minute_counter, 60 ;reset ; ================================================== ;  Count Down Sleep Timer ; ================================================== ; ;  Turned On by Entering Doze . . . sub ax, ax ;for resetting cmp sleep_timeout,al ;timeout used?? jz lb_dec ;NO mov al, sleep_count ;get sleep counter test al,al jz @F dec al ;dec sleep counter @@: mov  sleep_count, al ;reset ; ================================================== ;  Count Down low battery event Timer ; ================================================== ; ;  Rep count set by LB event detection lb_dec: cmp lb_event_rep,ah ;timeout used?? jz kbd_dec ;NO mov al, lb_event_count ;dec event counter test al, al ;already 0??? jz @F ;yes . . . dec al ;dec rep counter @@: mov lb_event_count, al ;reset ; ================================================== ;  Check For Keyboard Activity ; ================================================== even kbd_dec: test es:[di].HW_CAPS, HWC_KBACT jz pwr_dec ;doesnt support KB activity call oem_pm_kbd_activity? ;kbd active?? jnz nokbact ;yes, normal dbPC fTEST2+fTESTb “{circumflex over ( )}Y” ; ================================================== ;  Count Down Keyboard Timer ; ================================================== ; ;  Turned On by No Kbd Activity . . . cmp kbd_timeout,0 ,timeout used?? jz pwr_dec ;NO mov al, kbd_count ;get blank counter test al,al ;done . . . jz pwr_dec dec al ;dec sleep counter mov kbd_count, al ;reset to 0 jnz pwr_dec ;next counter or pm_flags, PM_VBLANK ;say its off . . . call oem_pm_blank_video ;blank the video jmp short pwr_dec nokbact: mov al,kbd_timeout ;reset counter mov kbd_count, al call oem_pm_reset_kbd_activity ;clear activity bit ; ================================================== ;  Count Down Power Off Timer ; ================================================== ; ;  Turned On by LB2 detection below, and powers off ;  if hw supports it ; even pwr_dec: test es:[di].HW_CAPS, HWC_POWER jz not_po ;doesnt support power off cmp pwr_off_timeout,0 ;Countdown enabled?? jz not_po ;NO dec pwr_off_count ;dec event counter jnz not_po dbPC fTEST2+fTESTb ”p” call oem_pm_power_off not_po: dbPC fTEST2+fTESTb ‘)’ page ; ================================================== ;  All Code Below is execute once a Second ; ================================================== even not_minute: ; ================================================== ;  Check and attend to the low battery indicators . . . ; ================================================== ; ;  Once a Second, we check the Battery Levels via ;  polling. Since some hardware generates an NMI, ;  we may not need to do this, Since the NMI will ;  be invoked at event time. ; ;  The Event Handler is assumed not to be re-entrant, ;  so it will not be re-entered until the first event ;  is handled. The next event will trigger as soon as ;  the PM_IN_LB_HANDLER flag is cleared. ; ;  Handler or no, the power off/Suspend Timeout is started ;  at Low, Low Battery detection. test es:[di].HW_CAPS, HWC_LB_NMI jnz ck_led ;supports nmi, dont need this call oem-pm_get_status ;get this stuff and ax, lb_event_mask ;need to attend to?? jz ck_lb ;no . . . test pm_flags, PM_LB_HANDLER ;have one?? jnz ck_ilbh ;yes . . . ck_lb: mov  lb_event_count, 0 ;clear rep count for re- entry . . . ck_lba: test ax, LBE_LB2 ;need to start power off?? jz ck_led ;no . . . jmp short pwr_ct ;still count power off ck_ilbh: dbPC fTEST2+fTESTb “v” test pm_flags, PM_IN_LB_HANDLER ;Blocked?? jnz ck_lb2 ;dont reenter cmp ax, lb_last_event ;same event as previously?? jnz ck_fevt cmp lb_event_count,0 ;time to repeat?? jnz ck_lb2 ;no . . . even ck_fevt: mov lb_last_event,ax ;save event or pm_flags, PM_IN_LB_HANDLER mov bl,lb_def_event_type ;default criteria push ax call lb_event_handler ;do it, LB flags in ax . . . pop ax mov bl, lb_event_rep ;reset mov lb_event_count, bl ;event rep time and pm_flags, not PM_IN_LB_HANDLER ; ================================================== ;  Start power off timeout/suspend machine ; ================================================== ck_lb2: test ax, LBE_LB2 ;need to start power off?? jz ck_led ;no . . . cmp pwr_off_count,0 ;started previously?? jnz ck_led ;yes . . . pwr_ct: mov ax, pwr_off_timeout ;start event test ax,ax ;immediate off/suspend??? jnz pwr_to ;no . . . test es:[di].HW_CAPS, HWC_SUSPEND jz ck_led ;doesnt support suspend dbPC fTEST2+fTESTb “o” call suspend ;suspend the machine . . . jmp exit_w_activity ;yes, run now . . . pwr_to: mov pwr_off_count, ax ;counter ; ================================================== ;  Handle LED Flash Cycles ; ================================================== ; ;  Some OEMs flash LEDs at different duty cycles to ;  indicate different operational conditions. ; ;  On/Off modulation is provided by this function. ; ;  LED flash cycles are handled ;  during the once per second loop ; even ck_led: test es:[di].HW_CAPS, HWC_LEDS jz ck_activity ;doesnt support LEDs cmp led_time_on, 0 ;LED cycle active?? jz ck_activity ;no dec led_next_event ;dec counter to next delta jnz ck_activity ;Non-zero, wait ; ==== LED event time, toggle state, inc counters call oem_pm_toggle_led mov al, led_time_off ;NO jz ck_led2 mov ax, led_cycle_count ;count infinite . . . test ax, ax ;yes . . . jz ck_led1 dec ax mov led_cycle_count, ax ;dec count every ON . . . jnz ck_led1 ;not timed out yet . . . mov led_time_on, 0 ;LED cycle NOT active ck_led1: mov al, led_time_on ck_led2: mov led_next_event, al ;reset ; ================================================== ;  Next, check if reentering from DOZE timer int ; ================================================== ; ;  Thread detection logic: ;  we made it to here, so lets see if we need to ;  exit to block again in DOZE, or to process a sleep ;  command, or perhaps enter doze. ; ;  If the DOZE flag is set, this means we entered the ;  timer hook from doze. we should then exit without ;  resetting the activity monitor, and let the DOZE thread ;  see if something happened to run Full Clock speed. ; ; ;  If the DOZE flag is not set, check and see if No activity ;  has been present for the DOZE timeout, and enter DOZE if so. ;  Otherwise reset the activity monitor. even ck_activity: test pm_flags, PM_SLEEP ;Req to sleep?? jz @F call sleep ;yes . . . call oem_pm_halt jmp wake ; run . . . @@: test pm_flags, PM_DOZE ;Were WE dozing . . . jz @F ;no jmp exit_wo_change ;YES, exit to code below ; ==== Next, check the activity Monitor ===== @@: dbPC fTEST2+fTESTb “I” call oem_pm_activity? ;turns ints off . . . jnz exit_w_activity ;yes, normal cmp doze_timeout, 0 ;doze allowed?? jz @F ;NO dec doze_count ;timeout?? jnz @F jmp go_doze @@: sti jmp exit_wo_change ; ================================================== ;  exits . . . ; ================================================== ; ;  Various exits to the COUNTER and DOZE threads . . . ; ;  Depending on Activity conditions even exit_w_activity: ; === Exit, and reset the activity monitor sti mov al, doze_timeout mov doze_count, al ; === Exit, and reset the activity monitor exit_w_clear: dbPC fTEST2+fTESTb “{circumflex over ( )}P” call oem_pm_reset_activity exit_wo_change: ret page ; ================================================== ;  go_doze ; ================================================== ; ;  At this point, we enter DOZE, having fulfilled the ;  criteria to enter that STATE ; even go_doze: mov al, sleep_timeout ;start sleep counter mov sleep_count, al ;each time doze re- entered or pm_flags, PM_DOZE ;in doze dbPC fTEST2+fTESTb “d” slow_cpu: call oem_pm_halt ;slow cpu, do halt ; ==== When we start up here, the sleep_check will already have ;  been run and taken the early return call oem_pm_activity? jz ck_sleep ;no, chk sleep and pm_flags, not PM_DOZE ;clear doze flag jmp exit_w_activity ;yes, normal ; ================================================== ;  Decrement Sleep Counters . . . ; ================================================== ; ;  At this point, we enter check the SLEEP counters ;  for criteria to enter that STATE. If not, reenter ;  the DOZE loop ; ck_sleep: sub al,al ;register zero cmp sleep_timeout,al ;sleep allowed . . . jz slow_cpu ;NO cmp sleep_count,al ;sleep time?? jnz slow_cpu ;no call sleep ;enter sleep mode and pm_flags, not PM_DOZE ;clear doze flag jmp exit_w_activity ;because we came out . . . page ; ================================================== ;  Sleep ; ================================================== ; ;  At this point, we enter SLEEP, having fulfilled the ;  criteria to enter that STATE ; ;  Save, in order: ;  Video Adaptor state ;  LCD state ;  8250 modes ;  LPT modes ;  Timer Mask ; ================================================== Sleep: dbPC fTEST2+fTESTb “S” push di push si push cx mov di,offset sleep_save_buf cld and pm_flags, not PM_SLEEP ;starting sleep req assume cs:code,ds:data0,es:pmdata push ds pop es mov ds,data0p ; ================================================== ;  save Display State ; ==================================================    call oem_pm_save_video_state ; ================================================== ;  save COM, LPT setups ; ================================================== mov dx, COM1 ;get COM1 call read_com mov dx, COM2 ;get COM2 call read_com mov dx, LPT1 ;get LPT1 call read_lpt mov dx, LPT2 call read_lpt mov dx, LPT3 call read_lpt call oem_pm_save_peripherals ;for private stuff . . . sleep_cpu: in al, PIC1 ;get timer mask stosb ;save or al, TMRINT out PIC1,al ;disable the timer interrupt assume cs:code,ds:pmdata,es:data0 push es pop ds mov es,data0p ;swap ES/DS mov ax,sleep_power_status ;turns off stuff . . . call oem_pm_turn_off_peripherals ;actually turns off stuff . . . ret page wake: ; ===== Restore Peripheral Status ================== ; ;  Because we are here, this means the wakeup key ;  was pressed, or an external interrupt came in. ;  Time to wake up . . . ; ; ;  Restore, in order: ;  Video Adaptor state ;  8250 mode ;  LPT mode ;  Timer Interrupt ; ================================================== cli mov ax,on_power_status ;What to turn . . . call oem_pm_turn_on_peripherals ;go do it mov si,offset sleep_save_buf ;start of save area cld ; ================================================== ;  Restore Display State ; ==================================================    call oem_pm_restore_video_state ; ================================================== ;  restore COM and PRN ; ================================================== mov dx,COM1 ;get com port call write_com mov dx,COM2 ;get com port call write_com mov dx,LPT1 ;restore lpt port call write_lpt mov dx,LPT2 ;restore lpt port call write_lpt mov dx,LPT3 ;restore lpt port call write_lpt call oem_pm_restore_peripherals ;for private stuff . . . push ds call set_ibm_timer ;restore ticks . . . pop ds lodsb out PIC1,al ;reenable interrupts pop cx pop si pop di dbPC fTEST2+fTESTb “G” ret page ; ================================================== ;  suspend ; ================================================== ; ;  Swap stacks, to ; ; assume cs:code,es:data0,ds:pmdata suspend proc ; ====== Save User Stack ===== cli mov ax,ss mov pm_save_ss, ax ;save stack mov ax,sp mov pm_save_sp, ax sti ====== Run On Resume Stack ===== mov ax, ds mov ss, ax ;setup resume stack mov sp, offset pm_resume_stack mov es,data0p mov reset_flag, FRESTORE call checksum ;check this memory mov pm_ram_chksum, ax ;save in pm_datat call sleep ;save it all . . . call oem_pm_suspend ;do it . . . ; ================================================== ;  pm_resume ; ================================================== ; ;  Cold Boot code jmps here with BP as no resume ;  return address . . . ; ;  check for a valid resume, do so ; ;  otherwise, jmp bp to cold boot code resume: mov es,data0p cmp reset_flag, FRESTORE jnz resume_err ; ===== PM data should still be valid ===== call get_pm_ds ;get datasg mov ax, ds mov ss, ax ;setup resume stack mov sp, offset pm_resume_stack call checksum cmp ax, pm_ram_chksum jnz resume_err call wake ;restore devices . . . ; ===== Restore User Stack ========= mov ax, pm_save_ss mov ss, ax mov sp, pm_save_sp ret ;to suspend caller resume_err: jmp bp ;return to do a hard reset suspend endp code ends end

TABLE 2 Program Listing A computer program embodiment of the software monitor for the power management unit appears in the following TABLE 2. ;===================================================== ; Do power management functions of int 16 h and int 8 h ; Copyright - 1990 Vadem, Inc. ; ; All Rights Reserved. ; ;   C: ;===================================================== ; code segment public ‘code’ assume cs:code org 100h start: jmp init even pp_addr dw 0378h old_i8 label dword i8_off dw 0 i8_seg dw 0ffffh old_i10 label dword i10_off dw 0 ; vector to old i10 i10_seg dw 0ffffh old_i16 label dword i16_off dw 0 ; vector to old i16 i16_seg dw 0ffffh sctr db 0 ; counter for timeouts two_ctr dw 12*182 ; 2 minute counter ;---- Interrupt 10h handler new_i10: call busy_check jmp old_i10 ;---- Interrupt 8 handler new_i8: call busy_check jmp old_i8 busy_check: cmp sctr,0 ; already in faxt mode? jz i8fast_mode sub sctr,50 jz i8fast_mode jnc i8z mov sctr,0 ;---- Switch to turbo mode here! i8fast_mode: cmp two_ctr,0 if timed out, do nothing jz i8z ; let IO monitor take over ;---- Two minutes have not gone by, turn it to ON! ---- dec two_ctr push dx push ax mov dx,0178h mov al,0c0h out dx,al inc dx in al,dx ; get status of chip mov ah,al and al,3 ; LSB 2 bits jz i8q ; if not ON, nothing to do! dec dx mov al,0c0h out dx,al inc dx mov al,ah and al,not 3 ; set to ON mode out dx,al i8q: pop ax pop dx i8z: ret ;---- Interrupt 16 interceptor new_i16: ;---- Time to switch from ON to DOSE mode? ---- push ax push dx mov dx,0178h mov al,0c0h out dx,al inc dx in al,dx ; get status of chip mov ah,al and al,3 ; LSB 2 bits jnz i16_dose ; if not ON, nothing to do! ;---- Check to see if time to go into DOSE... add sctr,24 jnc i16q ;---- Time to go into DOZE! dec dx mov al,0c0h out dx,al inc dx mov al,ah or al,1 ; set to dose mode out dx,al ; we are now in DOSE mode! jmp short il6setctrs ;---- We are already in DOSE mode, count faster! i16_dose: add sctr,200 jnc i16q i16setctrs: mov sctr,0ffh ; clamp it mov two_ctr,12 * 182 ; 18.2 Hz * 120 seconds i16q: pop dx pop ax jmp old_i16 ; do the original i16 init_str db ‘Power management controller version 1.00.$’ assume ds:code init: mov dx,offset init_str mov ah,9 int 21h mov ax,3508h int 21h mov i8_seg,es mov i8_off,bx push ds pop es mov dx,offset new_i8 mov ax,2508h int 21h mov ax,3510h int 21h mov i10_seg,es mov i10_off,bx push ds pop es mov dx,offset new_i10 mov ax,2510h int 21h mov ax,3516h int 21h mov i16_seg,es mov i16_off,bx push ds pop es mov dx,offset new_i16 mov ax,2516h int 21h mov dx,offset init_str+15 mov cl,4 shr dx,cl mov ax,3100h int 21h code ends end start

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention. 

What is claimed is:
 1. A power management unit for use in a computer system comprising a power supply, a plurality of computer system circuits including a CPU circuit, an input/output circuit, and a memory circuit, a computer system bus which couples the CPU circuit with said input/output circuit and said memory circuit, and a plurality of power control switches which couple the power supply to provide operating power to the plurality of computer system circuits, said power management unit comprises: an activity monitor which monitors activity of the computer system and generates an activity indicator signal reflective of said monitored activity; a mode controller responsive to the activity indicator signal and having at least three operating modes; and a power switching circuit comprising: a plurality of power control signal lines each for controlling one of said plurality of power control switches; a memory cell associated with each of the plurality of control lines wherein each of the plurality of power control lines is associated with at least one bit stored in said memory cell, said at least one bit being alterable depending upon said mode of operation; and power director means which in response to the mode of operation selectivity couples said plurality of power control lines to said memory cell associated with that power control line such that a signal is generated on the power control line that is dependent upon the state of the memory cell to which it is coupled, said power director means altering said at least one bit to change control data on that power control signal line in each of the three modes of operation, said plurality of switches are controlled by the power switching circuit and the power consumption of the computer system is controlled in response to the activity of the computer system. 